The stern tube sealing device refers to a device that uses white metal as the tail bearing, and maintains an appropriate fit gap between the stern shaft and the white metal stern bearing to ensure lubrication and cooling, reduce wear of the shaft and bearings, and reduce power consumption of the main engine. In order to prevent waste and pollution caused by lubricating oil leakage, and to prevent impurities such as mud, sand, and water from entering the bearings, good sealing devices are often used at the front and rear ends of the tail shaft tube.

To prevent seawater from entering the ship's interior along the propeller shaft and leakage of lubricating oil. A stern shaft sealing device must be installed in the stern tube device. For oil lubricated sealing devices, the main task of the head sealing device is to seal oil to prevent it from leaking inside the ship, while the stern sealing device bears the dual task of sealing water and oil. For water lubricated stern tube devices, only the head sealing device is installed, which is only responsible for preventing external water from leaking into the ship.

The function of the stern tube seals is to prevent water from entering the stern tube as well as to minimize the lubricant spillage to the marine environment and engine chamber.

At present, China mostly adopts the following four types of stern tube sealing devices:

(1) Rubber bowl type sealing device. It is a newly adopted type in recent years, which works more reliably and has a longer lifespan.

(2) Oil ring (oil ring) sleeve sealing device. It works reliably and has a long lifespan, but is generally only used for sealing the tail end of the tail shaft tube, while the head end uses a packing box.

(3) End face friction plate sealing device. This type of sealing device is often used on inland ships.

(4) J-shaped rubber ring sealing device. Composed of standard product J-shaped rubber bands. Due to its simple structure and small size, it is often used on small tugboats.